Frequency trajectory as a criterion for identifying core academic vocabulary

Frequency trajectory as a criterion for identifying core academic vocabulary

First Author: William Nagy -- Seattle Pacific University
Additional authors/chairs: 
Elfrieda Hiebert
Keywords: Academic Language, Vocabulary, Frequency
Abstract / Summary: 

Awareness of the impact of the language demands of schooling has led to attempts to identify words that are frequent in academic text and occur in a variety of content domains, but which are unlikely to be familiar to students. We propose frequency trajectory, the relative change of a word’s frequency over grade level, as a criterion for identifying such words. Words such as mom and nice have a negative trajectory, declining in frequency between primary grades and high school, whereas regard and assume increase in frequency over grade levels.

A measure of frequency trajectory was derived from grade-level frequencies in Zeno et al.’s Educators Word Frequency Guide. We compared the 500 words with highest values for frequency trajectory with the 500 words in Gardner and Davies’ Academic Vocabulary List (AVL) and with the 570 words in Coxhead’s (2000) Academic Word List (AWL), identifying words shared by one or two lists, and words unique to each list.

The Trajectory and AVL lists are more similar to each other, sharing 131 words, than either is to the AWL. The AWL shares only 40 words with the Trajectory list, and 87 words with the AVL. The words in the AWL are also more difficult than those in the other two lists, having a lower mean SFI, a higher mean age of acquisition, and a longer mean reaction time and lower accuracy rate in the British Lexicon Project lexical decision data.

On the basis of a comparison of these lists, and of the criteria they are based on, we conclude that frequency trajectory may by itself constitute a better characterization of core academic vocabulary than the other two lists; and whether or not it is adequate to serve as the sole criterion, should certainly be taken into account. Word lists should not dictate instructional practice; but they can help inform decisions about instructional practice both by teachers and by publishers of school materials.